Multispur fieldbus isolator arrangement

ABSTRACT

The present invention provides for a multispur fieldbus isolator arrangement having a trunk connection ( 23 ) and in which each of a number of spurs ( 210 ) is connected to the trunk ( 23 ) by isolator devices ( 24 ), where each isolator device ( 24 ) includes a removably mounted modular unit arranged for plug-in connection to the trunk ( 13 ) by means of a flameproof connection ( 29 ), and where a redundant isolator device can likewise be included for activation responsive to failure of an isolator device.

The present invention relates to a fieldbus isolated coupler, better known as a multispur fieldbus isolator or a fieldbus isolator, forming part of an Intrinsically Safe (IS) system for supplying power and/or signals into hazardous areas, and in particular to a multispur fieldbus isolator arrangement for supply of power and/or signals to a variety of different devices within an IS environment. In addition to the provision of simple fieldbus isolator devices for use in supplying an IS field device operating within a hazardous area, multispur fieldbus isolator arrangements are known having a trunk connection means for the connection of a trunk connection bus, and offering a plurality of spur outlets through which any appropriate number and variety of remote field devices can be supplied and/or addressed.

In such known systems, a variety of fieldbus isolator devices (also called fieldbus isolator units and fieldbus isolator device units) are provided, commonly with each one providing isolator protection for a plurality of spur outlets.

However, such known systems and arrangements prove disadvantageous and limiting with respect to matters of cost and ease of use and particularly where the multispur arrangement itself might have to be located within a potentially hazardous environment. In particular, such devices require extensive wiring connections which can lead to unnecessary size and complexity and labour-cost issues and the number, type, and general size of the enclosures required can also prove problematic and limiting. Should any changes/repairs to the system be required, it becomes necessary to power-down the fieldbus trunk. Also, surge limiter replacement carries the risk of adjacent-channel shorts and can require, depending on the specific characteristics of the particular environment, gas clearance for full power disconnection.

The present invention seeks to provide for a multispur fieldbus isolator arrangement having advantages over known such arrangements.

According to a first aspect of the present invention there is provided a multispur fieldbus isolator arrangement having trunk connection means and in which each of a plurality of spurs is connected to the trunk by isolatosr and with surge protector devices, wherein each isolator device comprises a removably mounted modular unit arranged for plug-in connection to the trunk by means of a flameproof connection so as to provide for a non-hazardous connection.

The provision of the isolator device in the form of a removably mounted modular unit assists greatly in reducing the wiring, and overall size of the arrangement and, in particular, use of the aforementioned flameproof connectors in connecting to the trunk allows for the advantageous use of a multispur arrangement within a potentially hazardous environment.

Advantageously, the trunk connection, modular isolator devices and surge protectors are disposed to be mounted onto the support means of the system.

In particular, since the support means can comprise a back plane, advantageously, the surge protectors can be removably mounted within the arrangement and without requiring neither removal of power from the trunk nor removal of power to the spur on which the surge protector is mounted.

In accordance with one aspect of the invention, the multispur arrangement can include redundant modular isolator device units arranged for interconnection to spur outlets associated with a failed unit.

In particular, the redundant modular isolator device can be arranged for interconnection to such spur outlets of the failed unit in a manner responsive to an indication of failure of the failed unit.

The invention can further provide control means for configuring the connection of the redundant modular isolator device units to the spur outlets.

In particular, each modular isolator device can be arranged to provide protection for a plurality of spur outlets.

Yet further, removably mounted trunk surge protector devices and/or removably mounted terminator devices can be provided and including flameproof connectors.

According to another aspect of the present invention there is provided a fieldbus isolator device arranged to be removably mounted in a multispur fieldbus isolator system and between a trunk connector and spur outlets, and comprising flameproof connector means for connection to the said trunk of the system.

Advantageously, the flameproof connector means comprise plug-connectors arranged for the removable mounting of the fieldbus isolator device.

Further, the fieldbus isolator device can include plug connector means for connection with surge protectors of the multispur fieldbus isolator system.

Yet further, the fieldbus isolator device can be arranged to be mounted by said flameproof connectors to support means of the multispur fieldbus isolator system which can comprise a back plane.

It should be appreciated therefore that the fieldbus isolator device can comprise a modular readily removable plug-in device.

The present invention can therefore advantageously allow for an effective “plug and play” solution to the provision of an appropriate number of fieldbus isolator devices within a multispur fieldbus isolator arrangement and which can readily provide for redundancy within the arrangement. The modular plug-in fieldbus isolator devices can be easily and quickly mounted as required and so maintenance of the device, and likewise the overall system arrangement, is likewise enhanced.

The whole system can therefore be readily tested, and appropriate adjustments and/or replacements made as required, before full installation.

As regards the location of the multispur unit within hazardous areas, it is considered that it can be readily mounted within a Zone 1 environment whilst still allowing for live disconnection/reconnection. Also, when compared with the current art, the overall volume of the enclosure, and indeed the number of enclosures required, is vastly reduced having advantageous cost implications.

Through the lack of manual input in building the system, and in particular removing the need for extensive wiring, the overall system is found to be more reliable and any required replacement of a isolator device can be achieved without disconnecting power or requiring gas clearance. Likewise, any spur surge protector insertion/replacement/removal, and/or any trunk surge protector insertion/replacement/removal, and/or any terminator insertion/replacement/removal, can be achieved while the system remains working.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a plan view of a conventional multispur fieldbus isolator arrangement;

FIG. 2 is a similar block diagram offering the same functionality as that of FIG. 1 but illustrating the multispur fieldbus arrangement according to an embodiment of the present invention; and

FIG. 3 is a similar block schematic diagram illustrating a multispur fieldbus arrangement according to another embodiment of the present invention.

Turning first to FIG. 1, there is provided a plan view of a typical conventional sixteen spur fieldbus isolator system arranged for connection to an input trunk, and for provision of output signals on sixteen spurs.

As will be appreciated from the discussion below, the sixteen spurs are divided into groups of four, each of which is provided with a signal from a four-spur isolator.

As illustrated in FIG. 1, there is provided an Exe terminal block 1 and associated trunk surge protector 2, and Exde safety flameproof switches 3 each of which feeds to a respective one of the four-spur isolators 4 which in turn have outputs connected to four spur outlets which are also fed by way of respective surge protectors 5 and terminal blocks 6.

Each of the four-spur isolators 4 is associated with a security cover 51 serving to prevent access to, and removal of, the connection without deactivating the flameproof switches 3. Also provided connected to the terminal block 1 is a terminator unit 8.

The actual external wiring to the spurs for the remote devices 10 leads from the respective terminal blocks 6. Also internal wiring and trunking 11 is provided for connection between external wiring 13 to the trunk and the terminal block 1 and wiring 11 is likewise provided for connection between the terminal block 1 and the safety flameproof switches 3. Further internal wiring 12 is provided for feeding from the flameproof switches 3 to the isolators 4 and internal wiring 14, 15 provides for connection between the barriers 4 and the terminal blocks 6 and also the surge protectors 5 and the terminal blocks 6. Also, each of the surge protectors 5 is fed directly by the external wiring 13 as illustrated.

As will be appreciated, the terminator units 8, trunk surge protector 2, flameproof switches 3 and associated wiring connections 11 as illustrated are provided within a separate enclosure 20.

The remainder of the system comprising the four-spur isolators 4 and associated surge protectors 5 and terminal blocks 6, and of course the associated internal wiring and elements of the external wiring 13 and internal wiring 12 as illustrated, is provided within a separate main enclosure 21.

As discussed previously, a variety of disadvantages arise in relation to such known systems not least of which is that removal of the various devices, and in particular the four-spur isolators 4 requires gas clearance and/or a power-down. Also, the use of the multiple flameproof switches 3 is found to be expensive and bulky.

In particular, the extensive internal wiring and trunking 12, 13, 14, 15 (as illustrated) disadvantageously necessitates the employment of wire, cable, two-ferrules per wire, and associated heat shrinking, trunking support, rows of terminal blocks, din rails and din rail supports which all serve to exaggerate the complexity and size of known arrangements. High labour costs are experienced in fitting the various mechanical parts of the system, in particular the din rails, and for stripping the wires, crimping the ferrules, heat shrinking the cable protectors that are all associated with the extensive wiring as illustrated in FIG. 1.

Any required changes cannot all be achieved on a live basis and the fieldbus has to be powered-down, which will effectively stop the plant in which the hazardous environment is found. Any required replacement of the surge protectors 5 will require disconnection of the spur and create a risk of adjacent-channel shorts. Further, any required replacement of the trunk surge protector 2 will require either gas clearance or disconnection of the power.

Also, it is a necessity that the intermediate Exe trunk connections 7 are changed by different personnel as compared with the remainder of the wiring and this leads to additional cost, and complexity and possibly down-time for the system.

Also, there is no scope for the provision of redundancy within the arrangement illustrated in FIG. 1.

Turning now to FIG. 2 there is provided a schematic block diagram of a multispur fieldbus isolator system according to an embodiment of the present invention.

Again, a trunk surge protector 22 is provided along with four-spur isolator devices 24, each associated with four surge protectors 25 from which extends external wiring of spur outlets 210 to the remote located field devices on each of the sixteen spurs. A terminator 28 is provided, and external wiring from the trunk arrives within the system, by way of the trunk surge protector 22.

The complete system is provided within a single enclosure 30 and each of the trunk surge protector 22, the four-spur isolator devices 24, spur surge protectors 25 and terminator 28 are removably mounted by way of plug-in connectors to a carrier 42, which can comprise a backplane 32 for the whole system. For example, as shown in FIG. 2, a removably mounted modular unit 35 can be a part of a isolator device 24. In such a case, the removably mounted module unit 35 can include the flameproof connectors 29 for connecting to the trunk 23 and one or more plug-in connectors 34 for connecting to a surge protector 25.

The backplane 32 includes the predefined electrical connection between the components as illustrated and thereby removes the need for the extensive wiring found in conventional systems.

Importantly, through the use of flameproof connectors 29, i.e. connectors arranged to provide for a non-hazardous connection, for connection of each of the isolator devices 24 with the external trunk wiring 23, the system itself can advantageously be located in a hazardous area as required.

The trunk surge protector 22, and terminator 28 can likewise be provided in a plug-in fashion by way of the flameproof connectors 29 illustrated to the carrier 32 without compromising the required level of at least “Zone 1” safety. Alternatively however, the terminator 28 can be provided as an integral part of the backplane carrier 32.

The overall size of the enclosure 30 of the embodiment of FIG. 2 can therefore be greatly reduced as compared with that employed in conventional systems such as illustrated in FIG. 1.

Another important point of advantageous comparison between the present invention and the prior art is clear from the comparison of FIGS. 1 and 2, in particular, the respective trunks 13 thereof. Within known systems such as that illustrated in FIG. 1, the trunk 13 is, as mentioned, connected to the terminal block 1 by way of jumpers or other appropriate means, in order to provide for yet further trunks 11 which, in turn, are connected to the Exed switches 3. The switchable trunks 12 are then, likewise in turn, connected to the isolators 4 by way of the intermediate Exe trunk connection 7.

Such prior art systems therefore require at least duplication and in some cases triplication, or more, of the trunk 13 in order to provide appropriate connection to the multiple isolators 4.

Turning now to the present invention, and the illustrated embodiment provided by FIG. 2, it will be immediately apparent that only one connection to the trunk 23 is required. The provision of the trunk surge protector 22 and its flame proof connectors 29 advantageously provide for the sole interface to the trunk 23 that is required for feeding all of the isolator devices 24 illustrated in FIG. 2.

Importantly, and as will be appreciated, the isolator devices 24 and indeed the surge protector 25, trunk surge protector 22 and terminator 28 can likewise be readily removed and replaced in a plug-in/plug-out manner whilst maintaining the required degree of safety and without requiring any down-time for the system, nor gas clearance, and without requiring only specific manual operations other than removal and replacement of the modular isolator devices 24.

Turning now to FIG. 3 there is provided a plan view of a further embodiment of the present invention and similar reference numerals to those found previously are employed. Here, two (or it readily could be more) separate carriers are provided each arranged for the removable mounting of two or more multi-spur isolator devices 24 and their associated spur surge protectors 25.

Connection between the carriers 32 so as to effectively achieve a unitary back plane is achieved by way of a flameproof jumper 37 which is arranged for grouping connection by way of flameproof connectors 29 engaging with sockets within the carrier 32 and which could otherwise be occupied by a terminator 28; one of which is illustrated in the right side carrier 32.

Any appropriate number of carriers 32 can then be connected in series so as to provide for any appropriate number of spur outlets from the fieldbus isolator system of the present invention.

As a further advantage of the present invention, an appropriate degree of redundancy can be introduced into the system by operation of a selection of one of the modular fieldbus isolator devices 24 as a redundant isolator device.

Such redundancy can readily be introduced into the present invention, and as illustrated in the embodiments of FIGS. 2 and 3, in view of the modular nature of the fieldbus isolator devices 24 in particular. Further, controlled- connectivity can be provided between the redundant isolator device 24 and the spur surge protectors 25 or spur outlets 210 associated with the failed isolator device 24 as required.

The failed modular isolator device 24 can then be readily and simply unplugged without requiring power down or gas clearance for thereby simple replacement by way of a replacement isolator device.

As can be further appreciated, the surge protectors 22, 25 of the invention can be readily replaced without effecting the whole operation of the system and the terminators 28 can be introduced, removed or replaced as appropriate during commission of the system whilst the system is live.

The modular nature of the isolator devices 24 allows for replacement without the requirement for disconnecting any other isolator devices, and the “plug and play” solution of the present invention greatly reduces the time that personnel need to be present on-site. Any further extension to the system, such as illustrated with reference to FIG. 3, can be performed without requiring power down or gas clearance, and the ready introduction of an appropriate degree of redundancy likewise allows for live repair relevant within the system.

In particular the invention advantageously employs the use of flameproof connectors 29 rather than screw terminals as found in conventional systems, and indeed rather than the use of flameproof switches 3 as currently known.

The carrier 32 provides a simplified and secure alternative option as compared with the large amount of wiring arising in the current systems and the use of live pluggable surge devices without disturbance of the functionality of the system provides a further advantage as does the use of the carrier board or back plane device for the redundancy functionality of the system.

It should of course be appreciated that the invention is not restricted to the details of the foregoing embodiments and that any appropriate configuration of modular fieldbus isolator devices and surge connectors, and indeed carrier boards can be provided as required and in offering an appropriate degree of Intrinsic Safety protection. Yet further, and with particular reference to FIG. 2, while a total of sixteen spurs is provided by way of four isolator devices 24 other configurations are readily possible. For example a single isolator device could be provided which itself offers the sixteen output spurs, or two isolator devices could be provided each offering eight output spurs. Any configuration is possible as required. 

1. A multispur fieldbus isolator arrangement for connection to a trunk and in which each of a plurality of spurs is arranged to be connected to the trunk by way of an isolator device, wherein the isolator device comprises an isolating bus coupler having a removably mounted modular unit arranged for plug-in connection to the trunk by means of a flameproof connection.
 2. The arrangement as claimed in claim 1, wherein each modular unit includes plug-in connectors for connecting with surge protectors associated with the spurs.
 3. The arrangement as claimed in claim 1, wherein the modular isolator units are arranged to be mounted onto a support member within the arrangement.
 4. The arrangement as claimed in claim 3, wherein the support member comprises a carrier.
 5. The arrangement as claimed in claim 4, wherein the carrier comprises a back plane.
 6. The arrangement as claimed in claim 3, wherein surge protectors are removably mounted within the arrangement.
 7. The arrangement as claimed in claim 1, including a trunk surge protector having flame proof connectors for providing an interface to the said trunk.
 8. The arrangement as claimed in claim 7 wherein each of the isolator devices is connected to the trunk by way of the said interface.
 9. The arrangement as claimed in claim 7, wherein the trunk surge protector device is removably mounted, having flameproof connectors.
 10. The arrangement as claimed in claim 1, including a redundant modular isolator device.
 11. The arrangement as claimed in claim 10, wherein the redundant modular isolator device is arranged for connection to the spur outlet associated with a failed isolator device.
 12. The arrangement as claimed in claim 11, wherein the redundant modular isolator device is arranged for the said connection to the spur in a manner responsive to the failure of the said failed unit.
 13. The arrangement as claimed in claim 11, and further including control means for configuring the said connection of the redundant modular isolator device to the spur outlets.
 14. The arrangement as claimed in claim 1, wherein a surge protector is removably mounted within the arrangement.
 15. A fieldbus isolator device comprising an isolating bus coupler arranged to be removably mounted in a multispur fieldbus isolator system and between a trunk and spur outlets, the isolating bus coupler including flameproof connector means for connection to the said trunk of the system.
 16. The device as claimed in claim 15, wherein the flameproof connector means comprise plug-connectors arranged for the removable mounting of the fieldbus isolator device.
 17. The device as claimed in claim 15, and including plug connector means for connection with surge protectors of the multispur fieldbus isolator system.
 18. The device as claimed in claim 15, and arranged to be mounted by said flameproof connectors to support means of the multispur fieldbus isolator system.
 19. The device as claimed in claim 15 and comprising a modular readily removable plug-in device.
 20. A fieldbus isolator device comprising: an isolating bus coupler comprising a removably mounted modular unit configured for plug-in connection to a trunk of a multispur fieldbus isolator system by means of a flameproof connection. 